POV: You clocked in seven hours of sleep last night and gave yourself a pat on the back. After all, you’ve met the oft-quoted “7-9 hours of sleep per night” recommendation.
Still, you can’t make it through the day without downing a few cups of coffee and resisting the urge to snooze. This makes you wonder, “Is 7 hours of sleep enough?” Or do you need more time in bed?
As surprising as this may be, seven hours of sleep is not enough for most people. Ahead, we take a look at how much sleep you might need instead and why it’s not your fault you thought this was your sleep need all along.
Sure, specific genes give us the ability to survive — and even thrive — on little sleep.
For instance, researchers at the University of California, San Francisco (UCSF) found that people with the NPSR1 gene mutation only need 4-5.5 hours of sleep per night. Meanwhile, those blessed with the DEC2 and ADRB1 gene mutations require only 5-6 hours of shut-eye.
Plot twist: Only a proverbial handful possesses these short-sleeping genes. In fact, the UCSF researchers mentioned that the NPSR1 gene mutation “is exceedingly rare, occurring in fewer than one in 4 million people.”
The likelihood of any of us surviving then on six hours of sleep or less is as rare as winning the lottery, but thriving on 7 hours of sleep is also statistically unlikely. Instead, your sleep need (the genetically determined amount of sleep your body needs) is probably closer to 8 hours and 10 minutes per night (plus or minus 44 minutes or so), meaning most of us need somewhere between 7.5-9 hours a night. A not-insignificant percentage of the population (13.5%) may need a longer sleep schedule of nine hours or more.
So, if you’ve underestimated your sleep need as seven hours all this while (don’t worry, you aren’t the only one!), you’re probably not getting enough sleep. Cue sleep debt — the amount of sleep you‘ve missed in the past 14 days relative to your sleep need. Sleep debt is the single number that best predicts how you feel and perform on any given day. And, because it’s a rolling tally of the sleep you’ve missed, how you feel today is not only a reflection of how much sleep you got last night, but how much sleep you’ve been getting. Confusingly then, even if your sleep need happened to be 7 hours and you got that much sleep last night, tiredness today could come from one or multiple prior days of less than 7 hours of sleep – more on this to come.
First though, how is it we’ve come to see 7 hours of sleep as not only acceptable but recommended?
If you’ve subscribed to the “7 hours of sleep per night” mentality, it’s not your fault. Here are six reasons we see 7 hours as enough sleep:
Well-meaning yet misguided sleep “guidelines” (we’ll explain the quotation marks) tell us seven hours is the amount of sleep we need without considering our unique chronobiology.
For instance, both the National Sleep Foundation and the joint consensus from the American Academy of Sleep Medicine and Sleep Research Society emphasize seven hours as the bare minimum of the optimal range of nightly sleep. Unfortunately, these recommendations fail to account for interindividual variability in terms of sleep need.
A 2018 review in the Journal of Nature and Science of Sleep sums up the conundrum: “Although sleep recommendations are a good tool for public health surveillance, they need to be adapted on a case-by-case basis (not a one-size-fits-all recommendation).” The review further highlighted that generalized sleep guidelines show “what is normal (or not) in the population and provide a yardstick for practitioners and educators when dealing with sleep-related issues” based on “observational studies using self-reported sleep duration.”
In other words, these recommendations aren’t really recommendations at all. They’re a reflection of how much sleep the population reports they’re getting, not what they biologically need.
Some people may argue recent research shows seven hours is the optimal sleep duration to keep your attention focused and your memory sharp.
That said, not all sleep experts agree on the latest finding.
In a CNN article, Russell Foster, director of the Sir Jules Thorn Sleep and Circadian Neuroscience Institute, cautioned that “taking the average of seven hours as the ideal amount of sleep "ignores the fact that there is considerable individual variation in sleep duration and quality.” He elaborated that "How long we sleep, our preferred sleep times and how many times we wake during the night varies hugely between individuals and as we age."
Most importantly, the sleep study highlights a correlative relationship rather than a causative one. In human-speak, that means seven hours of sleep is associated with good health and wellness, not necessarily the cause. It should also be highlighted that the study only covered middle-aged to older adults without featuring younger age groups.
You may have read it’s possible to get by on less sleep than your body needs by focusing on “the quality of your sleep” over any quantity prescriptions, even though scientists haven‘t agreed on an official definition for sleep quality.
However, the countless sleep “hacks” that inundate the web actually run counterintuitive to a good night’s sleep. Once you understand how sleep works, you’ll see why we can’t “hack” it, so to speak.
During sleep, the human body goes through 4-6 sleep cycles, each lasting about 90 minutes. Once you do the math, it’s easy to see how compressing your sleep duration into only seven hours per night cuts too close to the lower end of the sleep cycle estimate.
What’s more, sleep naturally progresses from deep sleep-dominant to REM sleep-dominant throughout the biological night. Cutting our sleep duration short — for example, sleeping for only seven hours instead of eight — doesn’t lead to a corresponding percentage decrease of 12.5% in REM sleep. The actual loss can be as high as 60-90%!
The bottom line is: quantity and quality sleep go hand in hand. “Quality” sleep is achieved by meeting your sleep need. And you can only keep your sleep debt low and your energy high if the sleep you’re getting to meet your need is healthy, naturalistic, “quality” sleep.
More on why sleep debt is the only “sleep score” that matters:
Older adults aren’t good sleepers compared to the younger populace of newborns, preschoolers, and school-aged children. (It’s a different story for teenagers and young adults.) Per a 2019 paper in the Journal of Current Geriatrics Reports, mechanisms associated with sleep homeostasis and the circadian rhythm (the internal biological clock) deteriorate with age, dampening the urge to sleep.
Consequently, the growing prevalence of sleep disorders (insomnia affects up to 75% of older adults) and poor sleep patterns have led to the mistaken belief that older people need less sleep. Other age-related health issues such as sleep apnea, cardiovascular disease, and high blood pressure also come with their fair share of sleep problems.
But insufficient sleep as we age doesn’t mean we need less sleep. As you’ll remember, our sleep need is genetically determined from birth and fixed past young adulthood. It’s just that naturalistic, healthy sleep becomes harder to come by over the years.
Misinformation about sleep isn’t the only reason we believe we can get by on 7 hours. Indeed, many of us may feel fine after sleeping seven hours, even though this isn’t our biological sleep need. Here’s the rub: while we may seem subjectively OK, we’ve actually objectively downgraded across all the parameters that matter — think our cognitive skills, emotions, and physiology.
Two reasons explain why we think we’re doing fine when we’re not.
Firstly, a lack of sleep ramps up our body’s cortisol production. Because cortisol is the alertness-boosting hormone, the unnatural hike in cortisol load masks the sleepiness that comes with too little sleep.
Secondly, our circadian rhythm continues to march on in the background even in the presence of high sleep debt. We still feel our two daily energy peaks that may lead us to believe we’re thriving on little sleep. In reality, though, these peaks could have been so much higher if we’ve slept more than seven hours and met our true sleep need.
Less an explanation of why 7 hours of sleep likely isn’t enough and more of a PSA: even if you think you’re getting 7 hours of sleep, there’s a good chance you’re not.
Indeed, research has shown that self-reported sleep is always less than objectively tracked sleep. Why? It’s a matter of what sleep scientists call “sleep efficiency,” the ratio of your total sleep time to the total amount of time you spend in bed.
As great as it would be to doze off immediately when our heads hit the pillow and stay asleep until the alarm clock goes off, as many of us sadly know, that’s not how sleep works. That’s because no one’s sleep efficiency is at 100 percent (anywhere above 85% is considered “good”). Going to bed at 11 p.m. and waking up at 6 a.m. doesn’t equate to exactly seven hours of sleep time. You likely spent some time falling asleep (sleep latency) and maybe even woke up once or more in the middle of the night (sleep fragmentation).
Once you know your true sleep need (more on that to come), we recommend adding a buffer of at least 30 minutes to account for time in bed that is not time spent asleep.
Only sleeping for seven hours when that isn’t your biological sleep need means you aren‘t feeling and functioning at your best when you need to.
Contrary to popular belief, we don’t have to pull an all-nighter to suffer from sleep loss. Simply getting one hour less than our sleep need, i.e. sleeping for seven hours instead of eight if that’s your true need, for ten consecutive days makes us as impaired as if we’ve stayed awake for 24 hours. Shockingly, research shows that’s akin to being as cognitively impaired as someone with a blood alcohol concentration of 0.10% — higher than the legal limit in every state.
Aside from the cognitive downgrades, expect:
With repeated sleep loss, we also predispose ourselves to an increased risk of chronic illnesses. Case in point: The earlier 2019 paper stated that older people with insomnia are more likely to experience health problems like obesity, diabetes, heart disease, mental illness, and even suicide. Substantial evidence links chronic sleep deprivation to:
If you both need and got 7 hours of sleep but still feel tired the next day, look to two likely culprits: sleep debt and circadian misalignment.
As we’ve covered, sleep debt is a measure of how much sleep you’ve missed out on over the past 14 days. Even if you met your sleep need last night, but had a busy previous week of late events and early morning meetings (or even just disrupted sleep), you’ll be carrying sleep debt. You can expect to feel off until that debt is paid back.
If you find you have more than five hours of sleep debt, you can catch up on sleep by:
If you’ve been meeting your sleep need and your sleep debt is low, but you’re still feeling tired throughout the day, there’s a good chance you’re suffering from circadian misalignment. That means you aren’t working with your internal body clocks and possibly living at odds with your chronotype (which determines your ideal sleep-wake preferences).
There are various ways circadian misalignment manifests, mainly through:
What are the most effective ways to get our clocks back in sync?
Now that you know seven hours of sleep doesn’t cut it for most people, determine how much sleep you need. Unfortunately, figuring that out on your own often involves wooly guesswork.
For a more reliable and accurate answer, use the RISE app. It leverages sleep-science-based models and the past 365 nights of sleep data tracked by your phone to learn your unique sleep biology and calculate your sleep need in hours and minutes.
What’s more, RISE uses phone motion-based sleep detection to monitor the start and end of your sleep schedule, night-time awakenings, and gauge your nighttime sleep duration. Weighing this number against your sleep need, RISE effectively calculates your sleep debt, so you know when to pay it down (you can use RISE to help you with that as well).
Getting the amount of sleep that’s right for you is the best way to feel and function your best. That‘s why RISE is the only tool you need for better sleep for better days.
The average sleep need stands at 8 hours and 10 minutes, with 13.5% of the general population requiring nine hours or more of shut-eye every night. As such, seven hours of sleep is typically not enough for the average individual.
During sleep, particularly slow-wave sleep, the human body releases muscle-building compounds like growth hormone and insulin-like growth factor-1. Not meeting your sleep need, i.e. only sleeping for seven hours, means you likely don’t get enough restorative shut-eye to build muscle, and may in fact, suffer from a loss in muscle mass.
Sleeping for only seven hours means you probably aren’t meeting your sleep need (the average sleep need is around 8 hours and 10 minutes). Short-sleeping is unfortunately associated with weight gain instead of weight loss, due to a bigger appetite, reduced energy, and elevated insulin resistance.
While research to learn more about sleep needs for teenagers is ongoing, we do know puberty forces a change in the timing of a teenager’s circadian rhythm, pushing it back by 2 hours on average. This means teenagers are biologically inclined to go to bed and wake up later than they did as younger children. Early school start times spell a tremendous amount of sleep debt for this age group.
Learn more about Rise for sales teams.
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